The objective of the proposed research is to understand the mechanisms by which nitric oxide (NO) regulates calcitonin gene-related peptide (CGRP) gene expression in trigeminal neurons. Serum levels of CGRP are elevated in alt forms of vascular headaches, including migraine. The neuropeptide CGRP is known to play a critical role in the underlying pathology of migraine due to its ability to regulate cerebral blood flow, mediate neurogenic inflammation, and relay nociceptive information to the CNS. Another agent implicated in migraine pathology is nitric oxide (NO). Glyceryl trinitrate, an exogenous NO donor, triggers migraine attacks, while blockade of NO synthesis aborts acute migraine attacks. The cerebrovascular affect of NO is thought to be mediated by the local release of neuropeptides from trigeminal neurons. In this proposal, I will test the hypothesis that NO directly stimulates CGRP gene expression and determine whether serotonergic anti-migraine drugs can repress the effect of NO. Studies proposed in the first specific aim will determine the effect of NO alone or in combination with other inflammatory mediators on CGRP release from trigeminal neurons and whether the anti-migraine drug sumatriptan can repress this effect. The second aim will focus on identifying the basal and NO-responsive regulatory sites in the CGRP promoter. Primary trigeminal ganglia cultures will be transiently transfected with CGRP-luciferase reporter DNA and reporter activity measured. The effect of sumatriptan on basal and NO-stimulated CGRP promoter activity will be determined. The third aim will elucidate the pathways involved in NO signaling in trigeminal neurons. Initially, specific cyclase and kinase inhibitors and activators will be used to identify the major pathway(s) involved in regulating the synthesis and release of CGRP. Further studies of individual pathways will utilize phosphospecific antibodies and signaling pathway detection kits. The effect of sumatriptan on NO-activated pathways will be determined. The overall goal of these studies is to gain insight into basal and NO regulation of CGRP gene expression in trigeminal neurons that may lead to the development of novel therapeutic strategies for migraine and other diseases involving neurogenic inflammation.